Damaged teeth may be repaired or replaced by crowns, bridge inlays, porcelain veneer or other common dental prosthesis. A successful repair requires accurate alignment and visual uniformity of the repaired tooth with the patient's other teeth. Typically, a model is made of the patient's teeth and the prosthesis is fitted to the model and adjusted to achieve proper alignment and visual uniformity outside the patient's mouth before the prosthesis is applied to the patient.
The model is typically formed by having a patient bite into a pliant casting material which cures to create a mold cavity having a negative impression of the patient's teeth and gums. The mold can be of all or any portion of the patient's gum line. A castable material is then poured into the negative impression to create a stone replica or dental model of the patient's teeth and gums, or a portion thereof. Once the castable material has cured, the mold is removed from the stone replica.
The dental model is typically connected to a base. Once connected to the base, the dental model may be cut and portions corresponding to damaged teeth may be removed and prosthesis fitted to the model of the damaged teeth. Once the prosthesis is fitted on a damaged tooth model, the damaged tooth model may be returned to the dental model base and alignment with adjacent teeth verified. Typically a model of the upper teeth is connected to a model of the corresponding lower teeth through their respective bases and an articulator. The articulator permits the technician to check the alignment of the prosthesis with opposing teeth. If the prosthesis does not align properly, the model of the damaged teeth may be removed and the prosthesis adjusted.
Dental model bases may be formed of plastic. Often, however, the dental model base is formed from a casting material. When a cast base is used, pins are fixed to the dental model. The pins protrude from the surface of the dental model that contacts the base. The pins may correspond to the teeth for which prosthesis are desired. The dental model is positioned adjacent a dental model base mold filled with uncured casting material. The pins protruding from the dental model extend into the uncured casting material. As the casting material cures, apertures are formed where the pins displace the casting material. After the casting material has cured, the base is removed from the mold. When the base has cured, the portions of the dental model corresponding to the pins may be disengaged from the base giving the technician access to the model of the damaged tooth. The detached segment may then be returned to the base and the pin reengage the aperture formed in the dental model base, assuring proper alignment with the dental model attached to the base.
Prior art bases used a relatively large quantity of casting material to support the dental model. Much of the casting material was required to give the base rigidity and stability. Casting material must be cured before it can be removed from the mold. Some distortions may result from the shrinkage associated with the curing of the casting material.
The cast base may have a slot formed in its anterior face to permit attachment to an articulator, such as the Vertex® articulator. Cast bases may also be attached to metal articulators by placing the side opposite the dental model adjacent the articulator and applying plaster to temporarily fix the cast dental model base to the articulator. Once the plaster cures, the dental model base is rigidly attached to the articulator.